Well on my 5.3 inch denali we used wood because I really wanted them to be straight. But now I used cardboard on my 54mm rocket and it workes perfectly. Depending on money and time I would say wood is better but it is also heavy.

Cardboard templates - 2 of them
Cut a 5" hole in it, with 3 slots radiating out from the hole, 120 degrees apart. You then line up the two templates with each other on the fins - perfectly straight, perfectly aligned fins every time. Tack the fins down, then take off the templates to fillet.

Most of the folks I know use cardboard ones. I have a rough set of them for HPR tube sizes made from regular corrugated box cardboard. They are easy to replace and you can lay them out perfectly with an old fashioned compass, a 360 degree protracter, a straightedge and a decent ruler. No big deal. For bigger birds and larger fins, I've used 2 at a time.

Warren

Agreed. So both of you feel that cardboard is stiff enough to give the fins good support? Chris, you said 120 degrees. I agree on that, too. But you have to account for the diameter of the fins; in other words, you use a jig to rest against the fins, but the 120 degrees is to fin center, so you have to delete the diameter of the fins from the 120 to be precise. That's the way I've always done it, and they come out straight. Correct?

Thanks, Warren. You know what rocket I'm talking about. This is why I posted. I was going to use wood, or masonite, and that'd be a pain. Listen, I really appreciate this from all. Thanks!

Bruce,

First you mark your center point, then you draw out your 120 degree (or 90 degree) centerlines, then you draw your circle for the airframe, then you draw a line on either side of those centerlines you drew 50% of the thickness of the fin. In the end, you cut out the circle for the airframe and little strips of cardboard the thickness of your fins at the centerlines. I make the slots as big as the largest part of the semi-span.

Warren

Warren,

Got it, easy to do, and it will save me a LOT of time. I ordered 8.9 oz. fiberglass cloth. As you said earlier in another post, and were you right!, carbon cloth is really hard to get ahold of right now because of the high professional demand. I feel that the glass I ordered will to the trick on the fins to MMT, and I have enough to add it to the fin to BT, or I'll use 3 oz. I won't know until I see what it looks and feels like. Still haven't gotten my extra components and fins from Wildman. That guy travels all over the place. Hope he gets my stuff together before he heads out to LDRS, Thanks again.

Bruce

Another material I have used besides cardboard is foam board. You can get it 20" x 30" in many arts and craft stores and sometimes as large as 30" x 40" in office supply stores. It is very rigid. I prefer to print out the pattern with a CAD program and use spray adhesive to attach it to the foam board but you can just draw it directly on the foam board.

Here is a jig I used on BDCR.
http://www.rocketryphotography.com/rockets/imgBDCR05.html

Doug

Why waste good money on good material. All mine were made from waste cardboard boxes.

Warren

I don't know Warren, we spend how many hundreds of dollars building and flying rockets? A couple of extra bucks to make the job easier sounds reasonable to me.

Doug

Go to an art store... they use mat board for framing pictures. I grab scraps. It is very rigid, and it cuts like a dream with a straightedge. I also keep all my old ones, so I rarely have to cut new ones anymore...